Telephone private branch exchange circuits



se,n 1e, am. 1,508,425?

J. F'. TGMEY ET AL 'rsLEPHonn PnvIvATz'BRANcH EXCHANGE CIRCUITS rn uw v. 1921 mvENToRs` ATTORNEY Patented Sept. 16, 1924,'

j'i UNITE' sr 'FF-IC JOHN TOOMEY AND HENRY E. IPHELPS, OIE" NEW YORK, N. Y., ASSIGNORS TO AMERI- CAN TELEPHONE AND TELEGRAP-I COMPANY, A. COR-PORA'IION 0F NEW YORK.'I

TELEPHONE .PRIVATE BRANCH EXCHANGE CIRCUITS.

Application filed July 7,

' provide a system of this character with a substation normally connected with the incoming trunk line, said trunk line extending toa plurality of operators or attendants positions, each of said positions having vthe same access to the trunk line.

ofi

Another object is to render the trunk line inaccessible to any of the operators or attendantspositions when the 'substation is in talking connection with said trunk line, thus insuring privacy at the substation.

Another object is to provide for automatic holding circuits vat each of the operators or attendants positions for thepu'r- `pose of holding the trunk connection until the substation or another attendant answers.

Another object is to provide signaling means 4at the various Voperatorsv or attendants positions for indicating the condition of the trunk line. A further vobject is to provide for the obviation ofI false signals on the operators or lattendants positions caused by condenser discharges, static impulses, Morse thumps or the like, as well as by dialing impulses when the private branch exchange is connected with a central ofiice where machine switching apparatus is employed.

These-objects, as well as other objects of the invention, may be attained by means of the apparatusset forth in the following description andillustrated in the accompanying drawing, the figure in which illustrates a circuit diagram of one embodiment of the invention.v

Referring to the drawing, 5 represents a jack 'at a central ofce, which has the usual equipment associated therewith, including the linesignal and also cut-off equipment. Connected with the jack 5 are line conductors 6 and 7, whichA lead tothe private branch i921. seiiai No. 482,988. g

exchange, the apparatus ofywhich isindi-v cated to the right of thefdotted lines. The private branch exchange'may be connected with manual or switching machinery controlled central ofii'ces. A substation set 8 and a plurality of attendants. positions, one of which is indicated at 9,- are connected to the line or'talking conductorst vand 7. A. relay 10 is provided at eacli attendants position for the purpose of'connecting the attendants? sets with the talkinglconductors 6 and 7. Each position is provided vwith a plurality of the customary keys adapted for talking and holding, one ofwhich vis illust trated at 11 at the attendants :position indicated at 9. A line lamp 12 and a holding and busy indicating lamp 13are associatedwith each key at each position for'the purpose ofv apprising theattendant thereatof the condition of the trunk. i ,i

Further details of the circuit and apparatus will now be clear from vthe following description of its operation.

Assumingthat a connection is desired be-l tween a main central oi'fice and a privatel branch exchange such asjillustrated in the drawing, the operator at said oilice will insert aplug connected lwith a cord circuit (not shown) into jack 5. rlhe operator at saidcentral office will then-cause'ringirig current to be transmitted in the usual way over the trunk comprising -conductors and 7 and throughthe substation 8, causing the bell thereat to ring. Ringing current, when j applied to the line conductors Gand 7, will also pass through the condenser 15 and winding vof ringing relay 16,-which is bridged across the line, causing saidrelay to operate.v

The operationof relay 16 closes 'a circuit ,g through its contact and left-hand winding of ringingrelay 17 thereby energizing the latter relay and bridging it across the line in `parallel with relay 16. l Thus, when ringing current comes lin over the trunk, itlasts for a comparatively long period, and relays 16 land 1,7 `operate in turn, while,v on the other hand, the transmission of momentary impulses, such as condenser discharges, static ioo i impulses, Morse thumps and' dialing imwill not continue sufficiently long yto pulses, i n

[it will be` evident,

operate y both relays.

therefore, that by this arrangement a guard,

is provided against false line signals at the attendants positions, which wiljlbe described presently. The operation of relay 17 closes a locking circuit through its right-hand winding and make contact, from battery and the back contact ot relay 18 to ground. The operation of relay 17 closes a circuit through its lett-hand make contact from ground, conductor 19, through the iilament of line lamp 12 at position 9, conductor 21, winding of relay 22 to battery. The closing of this circuit causes the lighting of line lamp 12 atrthe position indicated at 9, as well as corresponding lamps at each or" the other attendants positions, and also causes the operation ot relay 22. The operation of relay 22 closes a circuit trom ground, back contact of relay 23, make contact ot relay 22, winding oi' relay 24 to battery. The closing of this circuit operates relay 24, which in turn operates relay 23, by a circuit from battery, through the winding of relay 23, make contact of relay 24 to ground. The operation of relay 23 causes the operation of a device such as a buzzer 25, by circuit from ground, make contact oi relay 23, winding of buzzer 25 to battery. The operation of relay 23 also opens the operating' circuit of relay 24, causing it to release and in turn causing the release of relay 23. Relays 23 and 24 are slow release relays and operate and release alternately and cause the buzzer 25 to give a distinctive signal whereby the operators at each position are apprised of an incoming call.

.ln response to the lighting of lamp 12 an attendant Ytor instance at position 9 may answer the incoming call by operating key 11 to its talking` position, therebyclosing a circuit 'trom ground, winding et relay 10, contact 26 of key 11, conductor 27, winding ot relay 18 to battery. The closing of this circuit causes the energization ot relay 18,

which, upon operating, opens the locking circuit previously referred to, whereby relay 1? was held energized. rEhe cle-energization otrelay 17 opens the circuit previously described wl'iereby line lamp 12 was lighted and relay 22 was operated, thereby extinguishing line lamp 12 as well as corresponding lamps at the other positions and releasing relay 22. The operation of relay 18 closes a circuit through its front contact trom ground, conductor ,28, filament of lamp 13 to battery. The closing et' this circuit causes the lighting or the busy (or hold) lamp 13 and correspondinglamps at other positions. The closing of the circuit whereby relay 18 was operated, causes the energization of relay 10, which upon operating` connects the attendants telephone set at the position indicated at 9 with the talking -conductors, in an obvious manner, and also causes the operation cf' relay 29 over a circuit lirom ground, lower make contact of relay 10, winding et relay 29 to battery.

It, after answering the call the attendant desires to hold the connection, for inst-ance until the subscriber at station 8 answers. the talking key 11 is released from its talking position and operated to its holding position. The release olf key 11 from its talking position causes the release of relays 10 and 18. Relay 29, which is provided for the purpose of preventing Yliaise signals caused by the accidental operation et the keys, operated when relay 10 operated as just described. This relay is slow to release and remains energized momentarily and upon the operation et the key 11 to its holding position during this period a circuit is closed from ground, lower back contact of relay 10, make contact oi" relay 29, make contact 30 of key 11, conductor 3l., winding ot relay 32 to battery. The closing of this circuit energizes relay 32, which upon operating closes a circuit through its outer right-hand contact and through winding of marginal relay 33, thereby connecting said marginal relay across the line, thereby closing a circuit through said relay over the tip and ring conductors of the line and connected cord circuit (not shown) in a well understood manner. The marginal relay is provided for the purpose of preventing false line signals should the key 11 be operated to its holding position accidentally, and said relay will not operate unless a cord circuit is connected with the jack 5. Therefore said marginal relay will release in case ot an abandoned call or when the cord circuit is disconnected from the line. The marginal relay 33 under the present condition operates and closes a locking circuit from battery, winding and left-hand contact of relay 32, conductor 34, make contact of'marginal relay 33, conductor 35, back contact ot relay 18 to ground, relay 18 having released when key 11 wasoperated to its holding position. The operation oit relay 32 closes a circuit irom ground through its right-hand middle make contact, conductor 36, winding oi' relay 37, conductor 38, winding of relay 39 to battery. The closing of this circuit causes the operation of relays 37 and 39. The operation of relay 37 closes a circuit from ground, resistance 42, inner make contacts o1 relays 37 and 32, conductor 28, iilament oflamp 13 to ground. The closing of this circuit will not cause the lamp 13 to light because of insuiiicient current supply due to the inclusion or' the resistance 42 in the circuit. The operation ol relay 39 closes a` circuit through its ma -te contact from battery, winding of relay 40, make contact of relay 39, back contact of relay 41 to ground, causing the operation oft relay 40. Relay 40 upon operating causes the operation ot' relay 41 by a circuit from battery, winding of relay 41, make contact oi relay 40 to ground on the armatur.;` et relay 41. The operation of relay 41 opens the circuit just described for relay 40 and it releases and in turn releases relay 41, at which time relay 40 again operates. Thus the relays 40 and 41` alternately operate and release and 'each time the latter relay operates, a circuit is closed through its front contact from ground, make contacts of relay 37, inner right hand contact of relay 32, conductor 28, filament of (busy or) hold lamp 13 to battery. `The intermittent closure of this circuit shunts resistance 42 and causes the (busy and) hold lamp 13 to flash, thereby serving as an indication to the attendants at the various positions that the line is being helt.

Then the subscriber at station 8 responds to the incoming call, relay 43 will be operated by a circuit through its winding and through the switch hook at the substation, over the tip and ring conductors and through the tip and ring contacts of `jack 5 and through the connected cord (not shown) at the main exchange in a well known manner. The operation of relay 43 closes a circuit from ground through its make contact, co-nductor 44, winding of relay 18 to battery. The closing of this circuit causes the operation lof relay 18, and short-circuits :relay 10 at position 9 as well as corresponding relays at the associated positions, and yprevents the operators at any of the positions from obtaining access to the trunk at such time.

The operation of relay 18 also closes a circuit over conductor 28 which causesthe (holding or) busy lamp 13 to light, aspreviously described when the yattendant first answered.`

Should the substation 8 respond to the ringing of the bell thereat and answer an incoming call before an attendant at any of the positions answers fsaid call, relay 43 will operate and causethe operation ofrelay 18 as `just described, and the latter relay will function to short-circuit the relay 10 and corresponding relays at all the positions and also cause the deenergization of relay 17 and cause the substitut'on of the busy (or holding) lamp 13 in place of the line lamp 12 in a manner formerly indicated in connection with the operation of key 11.

At the termination of a call when the receiver at the substation 8 is returned toits hook, or when the attendant after answering a call has returned the key to normal, the relays release and the circuit vreturns to normal in an obvious manner. 'When the circuit returns to normal the supervisory lamp .in the connected cord circuit at the central office will light in a well understood manner, and the operator thereat in response to the lighting of. said lamp, will take down the connection.

Although this invention has been illustrated and described in connection with 'only'v one attendants position, it will be unsiti'ons may beconnected with the incoming trunk lne, and each position may 4have equal access to said trunk. 1:

It will be yobvious that the general principles herein disclosed may be embodiedl holding position, operators telephone apparatus, said switching means operating when thrown in talking position to close said circuit and to operate said relays whereby one of said 'relays will connect said operators set to said line andv the other of said relays will operate said second signaling means, and means associated with said line" and operative when the subscriberat 4said substation vresponds for'short-circuitiirst relay.

2. A trunk line interconnecting a central officey and `a substation, ringing responsive apparatus associated with said line, signaling means controlled thereby,a second siging the portion of said eircut includingisaid nal'ng means, a circuit including two relays connected in series, switching means adapted to' bethrown in talking lposition or in holding position, operators telephone apparatus, said switching means operating when thrown in talking vpostion to Aclose said circuit and to operate lsaid relays whereby one of said relays will connect-said ico operators set to said line, and the other of said relays will operate said second signaling means, means operative when rsaid swftching means are thrown in said holding position forvcausing said second signaling means to operate intermittently, and means,

associated `lwith said line and operative when the subscriberA at said substation responds for' short-circuitng the portion of said cir cuit including said firstrelay.

3. In. a telephone system, a main ex'- change, a private branch exchange, a trunk line interconnecting said main exchange and private branch exchange, asubstation at said branch exchange connnected directly with said trunk line,y a plurality of operators positions associated with said trunk,

a key at each position, means at each position responsiveto the operation of said key for connecting that position with said trunk` line, and means operable upon the removal ofthe receiver from its hook at said substation f'or short-cireuiting said last mentioned means and permitting access of said substation to said trunk line to the exclusion of said positions.

4L. In a telephone system, a main exchange, a private branch exchange including a substation and a plurality of operators positions associated therewith, signaling means at each ott' said positions., a trunk line interconnecting said main exchange and private branch exchange, means associated with said trunk line responsive to the application ot ringing current thereto for operating said signaling means, a key at each position, means associated with each key and responsive to the actuation thereof for connecting its position with said trunk, and means operable upon the removal of the receiver from its hook at said substation for permittingu access ot said station to 'said trunk line to the exclusion of said positions;

5. ln a telephone system, a main exchange, a private branch exchange includ.- ing a substation and a plurality of operators positions associated therewith, a trunk line interconnectin 0" said main exchange and private branch exchange, ringing responsive apparatus bridged across said trunk line, signaling means controlled thereby, a second signa-ling means, switching means at each position, means at each position re'- sponsive to the operation of said switching means for connecting` that position to said trunk line, a relay in series lwith said last mentioned means for controlling said ringing responsive apparatus and opera-ting said second signaling means, and means operable upon the removal ot the receiver from its hook at said substation for sliort--circuiting said last mentioned means and permitting access of said substation tofsaid trunk line to the exclusion of said positions.

6. ln a telephone system, a main Aexchange, a private branch exchange including a substation and a plurality of operators positions associated therewith, a Atrunk line for interconnectingr said main exchange and said private branch exchange, aringing responsive relay normally bridged across said trunk, a second ringing responsive relay bridged across said trunk line 'and in parallel with the first mentioned relay upon the operationof the latter relay,v signaling means controlled by said second relay, a second signaling means, and means common to said operators positions and said substation and responsive Vto the connection thereof with said trunk line for extinguishing the {irst mentioned signaling means anc operating said second mentioned signaling means.

7. In a telephone system, a main exchange, a private branch exchange including a substation and a plurality oit operators positions associated therewith, signaiing means at each of said positions, a trunk line interconnecting said main exchange and private branch exchange, means associated with said trunk line responsive to the application of ringing current thereto tor operating said signaling means, switching means at each operators position. adapted to be operated to a talking or holding position', means at each operators position responsive to the actuation of said switching means to a talking position tor connecting that position with said trunk, a ,relay responsive to the operation oi' said switching 'means to a talking position for extinguishing said signaling means a second signaling means responsive in a distinctive manner upon the actuation oif said switching means to a talking or holding position respectively, and means operable upon the removal o't' the receiver trom its hook at said substation for permitting access ot said station tosaid trunk to the exclusion ot said positions.

8. ln 'a telephone system, a main exchange, a private branch exchange including a substation and a plurality ot operators7 positions associated therewith, signaling means at each of said positions, a trunk line ,tor interconnecting said main exchange and private branch exchange, ringing responsive apparatus associated with the said trunk line for controlling said signaling means, a second signaling means, switching means adapted to be operated to a talking or holding position, means responsive to the actuation of said switching means to a talking position for connecting' said position with the said trunk line and extinguishing said first mentioned signaling means and substituting said second signaling means, means responsive to the operation of said switching means to a holding position tor establishing a holding bridge across said vtrunk and 'tor operating said second signaling means in a inanner distinctive from that iirst mentioned, and means operative when the subscriber at said substation responds for permitting access ot' said substation to said trunk line to the exclusion of the said positions.

9. In a telephoi'ie system, a main exchange, a private branch exchange including a plurality of associated operators telephone apparatus, a trunk line for interconnecting said main exchange and private branch exchange, switching means adapted to be operated to a talking or holding position, a relay responsive to the actuation of the switching means to a talking position Yfor connecting said telephone apparatus withsaid trunk line, and means controlled by said relay and responsive to the actuation of the switching means to a holding position for preventing accidental holding of said trunk line in busy condition.

10. In a telephone system,v a main exchange, a privatebranch exchange including a plurality of operators telephone appara-tus, a trunk line 'for interconnecting said main exchange and private branch eX- change, signaling means associated with each of said operators apparatus for indicating the busy or holding condition of said trunk line, switching means adapted to be operated to a talking or holding position, means responsive to the actuation of the switching ineans to a talking position for connecting said telephone apparatus with the trunk line, and ineans including` a marginal relay bridged across said trunk line controlled by Ithe operation ofthe switching means to a holding position for operating said signaling ineans, ysaid ineans being responsive only when the trunk line is in talking connection with the saidinain exchange.

In testimony whereof, We have signed our naines to this specification this 6th day of July 1921.

JOHN FQ Toor/LEY'. HENRY E. PHELPs. 

